Method for cooling containers and a cooling system for implementation of the method

ABSTRACT

The invention concerns a method for cooling containers, wherein cold is generated in a primary circuit containing a cooling medium. Cold is supplied via a heat exchanger to a cold carrier in a secondary circuit. The secondary circuit&#39;s cold carrier flows into a container through pipes with releasable couplings, transferring cold to the container through a heat exchanger. Cold is stored in one or more cold stores in the secondary circuit, in or outside the container, for subsequent emission in the event of an interruption in the cold supply. The invention also concerns a cooling system for implementation of the method.

The present invention concerns a method for cooling containers, whereincold is generated in a primary circuit containing a cooling medium andis supplied via a heat exchanger to a cold carrier in a secondarycircuit, where the secondary circuit's cold carrier flows into acontainer through a heat exchanger.

The invention also concerns a cooling system comprising a primarycircuit with a cooling medium for generating cold, a heat exchanger forsupply of cold from the cooling medium in the primary circuit to coldcarrier in a secondary circuit, the secondary circuit comprisingreleasable couplings for connecting to a container, the containercomprising a heat exchanger for WO93/23712 discloses a method forcooling containers, wherein cold is generated in a primary circuitcontaining a cooling medium and is supplied via a heat exchanger to acold carrier in a secondary circuit, wherein the secondary circuit'scold carrier flows into a container through pipes with releasablecouplings, transferring cold to the container through a heat exchanger,and wherein cold is stored in cold stores in the secondary circuit.

BACKGROUND OF THE INVENTION

There are previously known cooling systems for cooling containers inconnection with transport of food such as fish and the like, where thecold is generated by a primary circuit and transferred to a secondarycircuit. An appropriate cold carrier in the secondary circuit, normallybrine, transfers the cold into transportable containers, thus coolingtheir contents. The containers are exposed to cooling in the coolingcircuit for as long as possible, whereupon they are disconnected fromthe circuit for further transport, e.g. by trailer or rail, on the finalstage of the journey to the recipient.

Another known method is the use of transport containers with a store ofa cold carrier, e.g. ice or dry ice, where the ice or the dry ice isplaced in the container together with the goods which require to becooled, and give off their cold during that part of the transport whenthe container is not connected to the cooling circuit.

In the known cooling system there is a limit to how long a transportcontainers can be located outside the cooling system before the contentsare warmed to an unacceptable temperature. Alternatively, the coolingmedium in the form of ice or dry ice requires to be placed in thecontainer manually or by other means at the same time as the goods areplaced therein, which entails extra work and increased costs.

The object of the present invention is to provide a method for coolingcontainers and a cooling system where the containers can be kept cold ina simple manner without the supply of cold from the cooling system.

This object is achieved with a method and a cooling system of the typementioned in the introduction, characterized by the features which areindicated in the claims.

SUMMARY OF THE INVENTION

In this patent application the terms "emit cold", "supply cold" and"transfer cold" are used instead of the more correct "supply heat","emit heat" and "transfer heat". This terminology has been chosen inorder to make the description easier to understand.

The invention therefore consists of a cooling system consisting of aprimary circuit and a secondary circuit connected to a heat exchanger,where the cold is generated in the primary circuit in the known manner.The cold is transferred from the primary circuit to the secondarycircuit via the heat exchanger, where the cold is passed to a containerby means of a cold carrier. The secondary circuit has one or more coldstores for storage of cold and emission of cold in the event of aninterruption in the cold supply. This interruption may be due tooperational problems or a failure of the energy supply to the coolingsystem, or it may be an interruption in the cold supply resulting fromthe disconnection of the container from the cooling system.

In a preferred embodiment one of the cold stores is located inside thecontainer, with the result that the container is self-sufficient in coldemission during transport but a cold store may be located either insideor outside the container. It will, therefore, be understood that theprinciples of cold storage and emission described herein may be appliedto methods and systems for storing cold either inside or outside thecontainer.

The cold carrier is pressurized carbon dioxide (CO₂). This is a coldcarrier which affords moderate dimensions, small volume and no corrosionin the pipe system. The cold store or cold stores may consist of dryice, which can be generated directly form the carbon dioxide by reducingits pressure. The dry ice can be stored in a separate compartment in thecontainer for subsequent emission of cold when the dry ice turns intocarbon dioxide in a gaseous state, which can be done by the emission ofthe carbon dioxide directly into the container's atmosphere.

The cold store may also consist of an enclosed quantity of pressurizedcarbon dioxide. When the pressure of the carbon dioxide is reduced, dryice is produced, which can then emit its cold into the container in thesame manner as that described above.

When a cold store is employed in the secondary circuit some carbondioxide will have to be consumed, thus making it necessary to replenishwith new carbon dioxide. Since it is natural to employ the coolingsystem in connection with transport means with internal combustionengines, such as ships, this carbon dioxide is preferably supplied bymeans of a carbon dioxide generator which generates carbon dioxidereceived from the internal combustion engine's exhaust gases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow chart of a system for cooling a container inaccordance with the principles of the present invention; and

FIG. 2 is an alternative embodiment of the system of FIG. 1,schematically showing an internal combustion engine for providing asource of carbon dioxide to the system, as a cold carrier, in accordancewith the principles of the present invention.

A cooling system 1 consists of a primary circuit 2 and a secondarycircuit 3. The primary circuit 2 is of a known type and contains acooling unit 4 for generating cold. The cold is transferred to thesecondary circuit 3 through a heat exchanger 5. In the secondary circuit3 a cold carrier in the form of pressurized carbon dioxide flows througha pipe system 6 in the direction indicated by the arrow P. A circulationpump 7 passes the new carbon dioxide through the heat exchanger 5 forcold absorption from the primary circuit, and on through a cold store 8where cold can be emitted for storage, for subsequent emission back tosecondary circuit. The cold carrier flows on through a releasablecoupling 13 into a container 9 with goods (not shown). The container caneither flow into a cold store 11, which will be described in more detaillater, or it can flow into a heat exchanger 12 for emission of cold tothe container 9 by means of a fan 16. From the heat exchanger 12 thecold carrier can flow out of the container through a new releasablecoupling 13 and on to the circulation pump 7.

The two cold stores 8 and 11 are only illustrated schematically in thefigure, and may be designed in many ways. Nor does the figure showvalves, instruments and other components which are necessary for acomplete cooling system, since these other components are of a knowntype, and are of no consequence for the invention.

The cold stores 8 and 11 may consist of dry ice, and are supplied withcold by the controlled release of the secondary circuit's carbondioxide, the carbon dioxide thereby forming dry ice as the pressure isreduced. Cold is emitted from the cold stores when the dry iceevaporates, forming carbon dioxide in gaseous form during emission ofcold. In the cold store 8 this cold is used to cool the liquid carbondioxide which is located in the pipe system. In the cold store 11, whichis in communication with the interior of the container, the cold can beemitted in several ways: the cold can be transferred from the carbondioxide in gaseous form to the carbon dioxide in the pipe system, thecarbon dioxide in gaseous form to the carbon dioxide in the pipe thecontainer, or carbon dioxide in gaseous form can be led via an outlet 15into that part of the container which contains the goods, thus coolingthem directly. This latter method is advantageous for the container'satmosphere, since the carbon dioxide will reduce the growth ofmicro-organisms and contribute to the preservation of the foodstuffs.

The cold stores 8 and 11 can also consist of enclosed quantities ofpressurized carbon dioxide. A store of this kind can be achieved bymeans of a pressure vessel, or by using pipes and manifolds whichalready exist in the container, perhaps increasing their dimensions.This latter alternative is considered to be advantageous, since itprovides a simple and reasonably priced version of the cold store. Coldis emitted by pressure reduction under the controlled release of aportion of the carbon dioxide, thus forming dry ice. The cold can thenbe transferred as described above.

When the cold stores 8 and 11 are used, carbon dioxide will be consumedin the secondary circuit. Hence, in order to maintain the operation thesupply of carbon dioxide has to be replenished. In the embodiment in thefigure this is done by means of a CO₂ generator 14. The CO₂ generatormay preferably be based on membrane technology, being supplied withexhaust gasses from an internal combustion engine 17. The exhaust gasesare passed through the membranes, and due to the properties of themembranes, CO₂ is separated from the other exhaust gases. The CO₂generator further contains a compressor which pressurizes the carbondioxide before it is supplied to the secondary circuit.

In the above the invention has been explained with reference to aspecific embodiment described by means of a schematic flow chart. Theprocess can be advantageously controlled by a microprocessor (not shown)which receives information from instruments and a control console,controlling the process by means of controlled valves. Thus it isobvious that a number of different possibilities exist forinstrumentation, control and localisation of valves in the process.Similarly it is obvious that the pipe system can be designed in otherway, the pump 7, e.g., and the supply of carbon dioxide from the CO₂generator 14 being placed in other locations, there can be connectionsfor more containers 9, more cold stores 8 can be provided in thesecondary circuit, and bypass lines can be provided around the differentcomponents.

The cold emission from the dry ice stores can be self-regulating, thecold in the secondary circuit normally being kept at a level where theevaporation of carbon dioxide from the dry ice is zero or minimal.Should the temperature rise in the container the evaporation willincrease by itself, and the carbon dioxide in gaseous form will cool theinterior of the container. In this manner a reasonably priced andreliable regulation is obtained of the cold emission from the coldstores.

I claim:
 1. A method for cooling a container, comprising:generating coldin a primary circuit containing a cooling medium; supplying said cold toa cold carrier in a secondary circuit via a first heat exchanger;storing at least part of said cold from said secondary circuit in a coldstore; emitting from none to all of said cold from said cold store;carrying said cold in pressurized carbon dioxide, through releasablycoupled pipes, into a container using said secondary circuit;transferring said cold from said secondary circuit to said container viaa heat exchanger; and repeating said supplying, storing, emitting,carrying, and transferring.
 2. A method according to claim 1, wherein insaid storing at least part of said cold is stored inside said container.3. A method according to claim 2, wherein said storing comprises:formingdry ice by reducing the pressure of the carbon dioxide; and wherein saidemitting comprisesallowing said dry ice to evaporate.
 4. A methodaccording to claim 3, further comprising:receiving the exhaust gas froman internal combustion engine; generating carbon dioxide from saidexhaust gas; and replenishing carbon dioxide of said secondary circuitwith carbon dioxide generated by said generating.
 5. A method accordingto claim 2, wherein said storing comprises enclosing a quantity ofcarbon dioxide and said emitting comprises reducing the pressure of saidquantity of carbon dioxide.
 6. A method according to claim 5 whereinsaid emitting further comprises forming dry ice and allowing said dryice to evaporate.
 7. A method of according to claim 5, furthercomprising:receiving the exhaust gas from an internal combustion engine;generating carbon dioxide from said exhaust gas; and replenishing carbondioxide of said secondary circuit with carbon dioxide generated by saidgenerating.
 8. A method according to claim 1, wherein an said storing atleast part of said cold is stored outside said container.
 9. A methodaccording to claim 8, wherein said storing comprises:forming dry ice byreducing the pressure of the carbon dioxide; and wherein said emittingcomprisesallowing said dry ice to evaporate.
 10. A method according toclaim 9, further comprising:receiving the exhaust gas from an internalcombustion engine; generating carbon dioxide from said exhaust gas; andreplenishing carbon dioxide of said secondary circuit with carbondioxide generated by said generating.
 11. A method according to claim 8,wherein said storing comprisesenclosing a quantity of carbon dioxide andsaid emitting comprisesreducing the pressure of said quantity of carbondioxide.
 12. A method according to claim 11 wherein said emittingfurther comprises forming dry ice and allowing said dry ice toevaporate.
 13. A method of according to claim 11, furthercomprising:receiving the exhaust gas from an internal combustion engine;generating carbon dioxide from said exhaust gas; and replenishing carbondioxide of said secondary circuit with carbon dioxide generated by saidgenerating.
 14. A system for cooling a container comprising:a primarycircuit having a cooling medium for generating cold; and a secondarycircuit, said secondary circuit containing pressurized carbon dioxidefor carrying said cold and having a first portion and a second portion,said first portion being releasably coupled to said second portion,wherein:in said first portion of said secondary circuit, saidpressurized carbon dioxide of said secondary circuit is in thermalcommunication with said cooling medium of said primary circuit toreceive cold from said primary circuit; said second portion is disposedat least partially within said container; said second portion is inthermal communication with said container to supply cold to saidcontainer; and said first and second portions of said secondary circuittogether comprise:a cold store for storage of cold and emission of coldin the event of an interruption in the cold supply; and a means ofconducting said cold carrier from said primary circuit and said coldstore to said container.
 15. The system of claim 14 wherein said coldstore is connected to said second portion or said secondary circuit. 16.The system of claim 15 wherein said cold store is disposed inside saidcontainer.
 17. The system of claim 16 wherein said cold store comprisesan enclosed quantity of pressurized carbon dioxide that emits cold whenpressure of said carbon dioxide is reduced.
 18. The system of claim 15wherein said cold score comprises dry ice.
 19. The system of claim 15wherein said dry ice is generated by a reduction in the pressure of saidcarbon dioxide.
 20. The system of claim 15 wherein said dry ice of saidcold store is in communication with said interior of said container andis able to provide carbon dioxide to said atmosphere of said interior.21. The system of claim 14 wherein said cold store is connected to saidfirst portion of said secondary circuit.
 22. The system of claim 21wherein said cold store comprises dry ice.
 23. The system of claim 22wherein said dry ice is generated by a reduction in the pressure of saidcarbon dioxide.
 24. The system of claim 21 wherein said cold storecomprises an enclosed quantity of pressurized carbon dioxide that emitscold when pressure of said carbon dioxide is reduced.